Generating station transformer cooling arrangement



March 24, 1959 e. w. CLQTHIER 2,379,408

GENERATING STATION TRANSFORMER COOLING ARRANGEMENT Filed Feb. 6. 1956 WWW a/wumkort SM'LA-OM 211mm United States Patent GENERATING STATION TRANSFORMER COOLING ARRANGEMENT Gordon W. Clothie'r, Milwaukee, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Application February 6, 1956, Serial No. 563,467

13 Claims. (Cl. 307-83) This invention relates in general to power generating and transmission systems in which power transformers are employed to step up the voltage from the generating station generator to the transmission lines, and in particular to an improved cooling system for such transformers.

Power transformers are usually employed in a transmission system to step up the voltage from a generating station generator so a that power may be transmitted through the systems lines under high voltage and low current conditions thereby resulting in lower losses in the transmission lines. The amount of transformer capacity required bya particularsystem depends on the characteristics of'thegenerating station generator and various operating conditions of the system and hence is predetermined by methods well known in the art. Once the transformer capacity of the system is determined, serious consider'ation is always given to the type of transformer arrangement which is to furnish this capacity because if for some reason the selected arrangement is rendered inoperable, no power can be transmitted from the generating station. Hence, one factor. which influences the selection of a particular transformer arrangement for stepping up the; generator voltage is the reliability of the transformer arrangement. Other factors which are equally important in the selection of a particular transformer arrangement for a generating station are'the operating efiiciency of the arrangement and the amount of capital which must be invested in thearrangement.

Various transformer arrangements have been suggested in the priorart, for obtaining the required transformer capacity in a power transmission system but each of the suggested arrangements. have one or more disadvantages. For example, inone suggested arrangement the transformer capacity of the transmission'system is obtained by one large three phase power transformer provided with an externally disposed cooling system. The transformer has a load capacity equal to the transformer capacity required by the transmission system. The transformer has a cooling system andis designed so that the heat radiating capacity of the cooling system is coordinated with the heat generating capacity of the transformer to obtain an economic design compromise for the required load capacity of thetransformer.

The use of one large three phase power transformer to obtain thetransformer capacity required by the system has manyfadvantages from the operating efliciency and initial investment standpoints. However, from a reliability standpoint it has a serious disadvantage in that if the transformer or its cooling system is rendered inoperative for anyv reason, no power can be transmitted from the generating station. Another disadvantage is that the physical size of such a unit creates various problems in transporting the unit to its final destination.

Another suggested transformer arrangement for obtaining the required transformer capacity of the transmission system employs three separate single phase power transformers'with an additional unit as spare, in the event one of the three transformers is rendered inoperable.

This arrangement is advantageous from a reliability standpoint of the transmission system, but from the capital investment standpoint has the disadvantage that the investment is increased by more than one-third. The probability of increasing individual transformer failure is also increased since there are three separate transformers. Further, the operating efliciency of this arrangement is lower than where one larger three phase power transformer is employed.

' A third suggested transformer arrangement embodies a pair of three phase transformers each of which has a load capacity of one-half the predetermined transformer capacity required by the'transmission system. With this arrangement, if one of the units is rendered inoperable for any reason, the transmission system may operate at fifty percent full capacity through the other transformer. This arrangement is not as economical as the use of a single large three phase power transformer both from the capital investment standpoint and operating efliciency standpoint but has some advantages from a reliability standpoint, since if one transformer fails the system can function at reduced capacity. On the other hand, it is more economical from capital investment and operating efliciency standpoints than an arrangement which requires four single phase transformers, but less advantageous from a reliability standpoint.

' A modification of the third suggested transformer arrangement has also been suggested in the prior art and that is to design each of the transformers so that their individual load capacities are greater than half the predetermined transformer capacity required by the system. Thus if one transformer should fail, the capacity of the transmission system need only be reduced to the capacity of one transformer. This of course increases to some extent the reliability of the transmission system but also increases considerably the capital investment. Further it results in idle capacity for both transformers when the transformers are operated under normal conditions.

According to the present invention an arrangement of two three phase power transformers is provided for a power transmission system in which many of the disadvantages of the prior art are eliminated. The improved arrangement employs a pair of transformer assemblies whose combined load capacities furnish the predetermined transformer capacity required by the transmission system. Each of the transformer assemblies comprises a three phase power transformer provided with an externally disposed cooling system. The transformers may have equal ratings so that the load of the system is divided equally between the assemblies, or they may have different ratings so that the system load divides between them in proportion to their individual ratings. To increase the reliability of the transmission system the improved arrangement further includes means for selectively interconnecting the cooling systems of the two assemblies so that in addition to sharing the electrical load on the transmission system in proportion to their ratings, the thermal load of the system may be divided between the transformer in proportion to their rating. The reliability of the transmission system is increased by the improved arrangement since if one transformer is rendered inoperative, the heat radiating capacity of the other transformer is increased. The increase in the heat radiating capacity of the one operable transformer allows that transformer to handle considerably more than fifty percent of the gencrating station capacity.

The reliability of the transmission system is further increased by arranging the individual heat exchangers in each cooling system so that they may be disconnected from their associate cooling system for repair and servicing.

It sometimes happens that a heat exchanger in one of the transformer cooling systems must be serviced or repaired, necessitating a predetermined reduction in load capacity for that transformer. Since both transformers must divide the load on the system in proportion to their ratings, the load capacity of the other transformer must also be similarly reduced, resulting in a proportionate reduction of the load capacity of the system.

However, with the present invention, the cooling system of both transformers are interconnected so that the required reduction in system capacity is less than heretofore required by prior art arrangements.

It is therefore an object of the present invention to provide an improved transformer arrangement for a power transmitting system.

A further object of the present invention is to provide in a generating station transformer arrangement having a pair of transformers associated through a common electrical load, means for associating the thermal loads of said transformers through their associate cooling systems.

Objects and advantages other than those mentioned above will be apparent from the following description when read in connection with the drawing in which:

Fig. 1 is a single line diagram of a power transmission system embodying the present invention;

Fig. 2 is a plan view of the improved transformer arrangement shown in Fig. 1;

Fig. 3 is a view in elevation of the transformer arrangement shown in Fig. 2; and

Fig. 4 is a view in section taken along the line IV-IV of Fig. 3.

Referring to the drawing, there is illustrated diagrammatically' in Fig. 1 a simple single line diagram of a power generating and transmission system which includes a generating station generator 11, transmission lines 12 and the improved transformer arrangement 14 for stepping up the voltage from generator 11 to transmission line 12.

The transformer capacity required by the system is predetermined by any of the methods known in the art and the predetermined capacity is furnished to the system by transformer arrangement 14. Th details of the electrical power connections from the generating station generator 11 to the transformer arrangement 14, and the details of the electrical power connections from the transformer arrangement 14 to the transmission lines 12 have been omitted from the drawing for clarity reasons, it being understood that any suitable connecting arrangement known in the art may be employed.

Fig. 2 illustrates schematically the transformer arrangement 14 shown diagrammatically in Fig. 1. Transformer arrangement 14 comprises generally a pair of three phase power transformers 16 and 17 which are provided with their own cooling systems 18 and 19, and

means for selectively connecting cooling systems 18 and 19 to either or both of the transformers 16 and 17.

The three phase power transformers illustrated are of any suitable type known in the art, and hence a. detailed description of their construction and operation does not appear necessary to an understanding of the present invention. Each of the transformers may have the same load capacity so that each assembly normally furnishes fifty percent of the transformer capacity required by the system. The transformers may also have unequal load capacities in which case the system load divides between the transformers in proportion to their individual ratings. In the illustrated embodiment it will be assumed that each transformer furnishes fifty percent of the transformer capacity required by the system in which case the transformers would be similar and have substantially the same rating.

The cooling systems 18 and 19 associate respectively with transformers 16 and 17 and are identical so only one is described in detail. Cooling system 18, as shown, comprises a plurality of heat exchangers 20 connected so that the cooling medium for transformer 16 flows from the transformer tank 22 to each heat exchanger 20 where it is cooled, and back to the tank 22 in a continuous cycle. Heat exchangers 20 are preferably of the type which allow the cooling medium to circulate through the heat exchanger by a thermal syphoning action, with means such as a pump 24 to provide forced circulation of the medium if additional cooling is desired. Also heat exchangers 20 are preferably of the type provided with auxiliary fans 25 to increase the rate of heat exchange between the transformer cooling medium and surround ing atmosphere-if still more cooling of the medium is desired. The cooling system may be either manually controlled or controlled automatically by suitable equipment associated with transformer 16 in response to the temperature conditions in the transformer. The cooling medium for transformer 16 is preferably oil although other fluids or gases may be employed.

Cooling system 18 associated with transformer 16 comprises six heat exchangers 20 which are arranged in two banks 27 and 28. Each bank of three heat exchangers is provided with means for connecting the heat exchangers 20 in fluid exchange relationship with the transformer tank 22. For bank 27 this means comprises a header 29 extending from the vicinity of the top of the transformer tank 22 and a second header 30 extending from the vicinity of the lower portion of the tank 22, each heat exchanger 20 being connected between the two headers 29 and 30. The other bank 28 of heat exchangers is connected "similarly to the tank by means of headers 31. and 32.

Suitable valves 34 are associated with the headers 2932 to connect them to the tank 20. Suitable valves 35 are also provided for connecting and disconnecting each heat exchanger 20 from its associated header. Transformer 17 and its associated cooling system 19 is similar to transformer 16 and cooling system 18.

Normally the cooling systems 18 and 19 operate in conjunction with their respective transformers 16 and 17 to enable each transformer to furnish fifty percent of the transformer capacity required by the transmission system; However, if for some reason one of the transformers is rendered inoperable, the improved transformer arrangement includes means for connecting the cooling system of the inoperable transformer in fluid exchange relationship with the operable transformer. additional cooling, the load capacity of the operable transformer may be raised to the neighborhood of seventy percent of the transformer capacity required by the system. This is accomplished with only a negligible increase in capital investment.

The connecting means, as shown, is relatively simple and comprises pipes or'conduits 38'interconnecting similar headers of the two cooling systems 18 and 19. Valve means 39 which are normally closed are associated with each conduit so that when both, transformers 16 and 17 areoperable each cooling system 18 and 1.9..is associated with its respective transformer, andwhen open, both systems 18 and 19 maybe associated with one transformer depending on the position of the valves 34.

The advantages of such a cooling arrangement are many. The reliability of the generating station is increased with only a negligible increase in capital investment. Further, it permits therepair and servicing of one transformer without unduly reducing the generating station output. The improved arrangement further permits greater flexibility in the use of'the heat exchangers 20 between the two transformers 16 and 17 thereby reducing the transmission system capacity less if one heat exchanger is inoperable. For example, if one heat exchanger were rendered inoperable in prior art arrangements the capacity of both transformers must be reduced since they share the electrical load equally, or at least proportionately. The capacity of the system is therefore reduced proportionally to the capacity obtained by With the one heat exchanger on each transformer. However, with the present arrangement the cooling systems 18 and 19 of transformers 16 and 17 are interconnected and the capacity of the transmission system need only be reduced in proportion to the loss of one-half of a heat exchanger.

While the improved transformer arrangement has been illustrated and described in connection with stepping up the voltage in a power generating and transmission system, it should be understood that the improved arrangement may also function to step down the voltage from a high voltage transmission system to a load consuming a large amount of power at a relatively low voltage. The operation of this modification is similar to that just described.

While only one embodiment of the present invention has been illustrated and described it will be apparent to those skilled in the art that modifications other than those shown may be made without departing from the spirit of the invention or from the scope ofthe appended claims. For example, such modifications: may include valve arrangements for the cooling-systems 18 and 19 in which the individual cooling systems are connected in hydraulic parallel relationship rather than in series relationship as illustrated in the preferred embodiment.

Similarly, various combinations of series and parallel hydraulic arrangements may be employed. In addition the number of heat exchangers may also be more or less than the number illustrated without departing from the spirit of the invention.

It is claimed and desired to secure by Letters Patent:

1. In combination with a power transmission system having a required predetermined transformer capacity, first and second transformer assemblies for furnishing said predetermined transformer capacity to said system in proportion to the individual ratings of said assemblies, each of said assemblies comprising a three phase power transformer having an externally disposed cooling system, means for directly connecting the said cooling system of one of said assemblies in fluid exchange relationship with the said cooling system of said other assembly to increase the load capacity of said transformer of said other assembly in the event said transformer of said one assembly is rendered inoperative, and means for disconnecting said transformers from their associated cooling systems.

2. In combination with a power transmission system having a required predetermined transformer capacity, first and second transformer assemblies each comprising a three phase power transformer having an externally disposed cooling system, each said assembly being operable to furnish fifty percent of said required capacity to said system continuously without damage to said transformers, means for directly connecting said cooling system of said first assembly in fluid exchange relationship with said cooling system of said second assembly, to increase the load capacity of said transformer of said second assembly beyond said fifty percent in the event said transformer of said first assembly is rendered inoperative, and means for disconnecting said transformers from their associated cooling systems.

3. In an electrical power generating and transmission system having a predetermined transformer capacity, the combination of first and second transformer assemblies for furnishing said predetermined capacity to said transmission system in proportion to their respective ratings, each of said assemblies comprising a three phase power transformer operable to step up the voltage from a generating station generator to the lines of said transmission system, and an externally disposed cooling system connected in fluid exchange relationship with said transformer; connecting means for selectively connecting the cooling systems of both said assemblies in fluid exchange relationship with the transformer of one of said assemblies in the event the transformer of said other assembly is rendered inoperative, and means for disconnecting said transformers from their associated cooling systems.

4. In an electrical power generating and transmission system having a predetermined transformer capacity, the combination of first and second transformer assemblies for furnishing said predetermined capacity to said transmission system in substantially equal amounts; each of said assemblies comprising a three phase power transformer operating to step up the voltage from a generating station generator to the lines of said transmission system, and an externally disposed cooling system connected in fluid exchange relationship with said transformer to cause the load capacity of said assembly to represent fifty percent of said predetermined transformer capacity; hydraulic connecting means common to the cooling systems of both said assemblies for selectively connecting both said cooling systems in fluid exchange relationship with said transformer of one of said assemblies in the event the transformer of said other assembly is rendered in operative, and means for disconnecting said transformers from their associated cooling systems.

5. In an electrical power generating and transmission system having a predetermined transformer capacity, the combination comprising first and second transformer assemblies for furnishing said predetermined capacity to said transmission system in substantially equal amounts; each of said assemblies comprising a three phase power transformer having a cooling system disposed externally of said transformer, said cooling system comprising a plurality of heat exchangers, header means for connecting said heat exchangers in fluid exchange relationship with said transformer, and means for disconnecting each of said heat exchangers from said header means; valve means common to the cooling systems of said assemblies for selectively connecting both of said cooling systems in fluid exchange relationship with the transformer of one of said assemblies in the event the transformer of said other assembly is rendered inoperable, and means for disconnecting said header means from said transformers.

6. In an electrical power generating and transmission system having a predetermined transformer capacity the combination comprising first and second transformer assemblies for furnishing said pretermined capacity to said system; each of said assemblies comprising a three phase power transformer having a cooling system disposed externally of said transformer, said cooling system comprising a plurality of heat exchangers, header means for connecting said heat exchangers in fluid exchange relationship with said transformer, forced fluid flow means for increasing the cooling capacity of said cooling system in response to thermal conditions of said transformer, and means for disconnecting each of said heat exchangers from said header means; valve means common to the cooling systems of said assemblies for selectively connecting both of said cooling systems in fluid exchange relationship with the transformer of one of said assemblies in the event the transformer of said other assembly is rendered inoperable, and means for disconnecting said header means from said transformers.

7. In an electrical power generating and transmission system having a predetermined transformer capacity, the combination comprising first and second transformer assemblies for furnishing said predetermined capacity to said system; each of said assemblies comprising a three phase power transformer having a cooling system disposed externally of said transformer, said cooling system comprising a plurality of heat exchangers, header means for connecting said heat exchangers in fluid exchange relationship with said transformer, forced fluid flow means associated with each of said heat exchangers to increase their respective cooling capacities in response to thermal conditions of said transformer, and means for disconnecting each of said heat exchangers from said header means; valve means common to the cooling systems of said as semblies for selectively connecting both of said cooling means; for disconnecting said header means from said transformers.

8. The combination recited in claim 7 in which each said heat exchanger includes means for increasing its rate of cooling in response to a second thermal condition of said transformer.

9. The combination recited in claim 8 in which the means for increasing the cooling rate comprises a plurality of motor drive fans.

10. In an electrical power transmission system having a predetermined transformer capacity, the combinationof first and second. transformer assemblies; each of said assemblies comprising a three phase power transformer connected electrically to said system, an external cooling system for said transformer comprising a plurality of coolers each of which are removably connected in fluid exchange relationship with. said transformer, said cooling system having a: maximum heat radiating capacity suflicient, to allow said transformer to furnish fifty percent ofv said predetermined capacity continuously without damage to said transformer; and valve means for selectively interconnectingthe cooling systems of said assemblies; in. the. event. thatv one of said, coolersxis rendered inoperable v, a v

11,: The combination. recited in claim 10 in which each saidcooling system includes means for increasing the rate of fluid exchange between said transformer and each of said coolers. 1

12. The combination recited in claim 11 in which each of. said coolers'is-forced air cooled in response to thermal conditions in its associated transformer.

13. In combination first and second transformer assemblies each comprising a three phase power transformer having an externally disposed cooling system, means for electrically connecting said transformers in parallel to supply a common load in proportion to their respective ratings, means for interconnecting said cooling systems in the event one of said transformers is rendered inoperable, andtmeans for. disconnecting said inoperable transformer from its associated cooling system.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT (OFFICE @ERTIHQATE GE @QRREGHUN Patent No. 2,879,408 March 2.4, 1959 Gordon W Clothier It is hereby certified that error appears in the printed specification oi the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 6, line 20, for "in operative read M inoperative Signed and sealed this 7th day of July 19590 (SEAL) T156551:

KARL Hi AXLINE ROBERT C. WATSOII Commissioner of Patents UNITED STATES PATENT OFFICE i @ERTIHCATE @F @QRRECZFWN i Patent No. 2,879,408

March 24, 1959 Gordon W. Clothier- It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below" Column 6, line 20, for "in operative" read. inoperative (SEAL) lttcst:

KARL Ha AXLINE ting Officer ROBERT C. WATSON Commissioner of Patents 

